package com.itcag.util.txt;

/**
  * Stemmer, implementing the Porter Stemming Algorithm
  *
  * The Stemmer class transforms a word into its root form.  The input
  * word can be provided a character at time (by calling add()), or at once
  * by calling one of the various stem(something) methods.
  */
public final class Stemmer {

    private char[] b;
    private int i;
    private int i_end;
    private int j;
    private int k;
    private static final int INC = 50;

    public Stemmer() {
        b = new char[INC];
        i = 0;
        i_end = 0;
    }

   /**
    * Add a character to the word being stemmed.  When you are finished
    * adding characters, you can call stem(void) to stem the word.
    */
    public void add(char ch) {
        if (i == b.length) {
            char[] new_b = new char[i+INC];
            for (int c = 0; c < i; c++) new_b[c] = b[c];
            b = new_b;
        }
        b[i++] = ch;
    }


   /** Adds wLen characters to the word being stemmed contained in a portion
    * of a char[] array. This is like repeated calls of add(char ch), but
    * faster.
    */
    public void add(char[] w, int wLen) {
        if (i+wLen >= b.length) {
            char[] new_b = new char[i+wLen+INC];
            for (int c = 0; c < i; c++) new_b[c] = b[c];
            b = new_b;
        }
        for (int c = 0; c < wLen; c++) b[i++] = w[c];
    }

   /**
    * After a word has been stemmed, it can be retrieved by toString(),
    * or a reference to the internal buffer can be retrieved by getResultBuffer
    * and getResultLength (which is generally more efficient.)
    */
   public String toString() { return new String(b,0,i_end); }

   /**
    * Returns the length of the word resulting from the stemming process.
    */
   public int getResultLength() { return i_end; }

    /**
     * Returns a reference to a character buffer containing the results of
     * the stemming process.  You also need to consult getResultLength()
     * to determine the length of the result.
     */
    public char[] getResultBuffer() { return b; }

   /* cons(i) is true <=> b[i] is a consonant. */
    private boolean cons(int i) {
        switch (b[i]) {
            case 'a':
            case 'e':
            case 'i':
            case 'o':
            case 'u':
                return false;
            case 'y':
                return (i==0) ? true : !cons(i-1);
            default:
                return true;
       }
    }

   /* m() measures the number of consonant sequences between 0 and j. if c is
      a consonant sequence and v a vowel sequence, and <..> indicates arbitrary
      presence,

         <c><v>       gives 0
         <c>vc<v>     gives 1
         <c>vcvc<v>   gives 2
         <c>vcvcvc<v> gives 3
         ....
   */
    private int m() {
        int n = 0;
        int i = 0;
        while(true) {
            if (i > j) return n;
            if (! cons(i)) break; i++;
        }
        i++;
        while(true) {
            while(true) {
                if (i > j) return n;
                if (cons(i)) break;
                i++;
            }
            i++;
            n++;
            while(true) {
                if (i > j) return n;
                if (! cons(i)) break;
                i++;
            }
            i++;
        }
    }

   /* vowelinstem() is true <=> 0,...j contains a vowel */
    private boolean vowelinstem() {
        int i;
        for (i = 0; i <= j; i++) if (! cons(i)) return true;
        return false;
    }

   /* doublec(j) is true <=> j,(j-1) contain a double consonant. */
    private boolean doublec(int j) {
        if (j < 1) return false;
        if (b[j] != b[j-1]) return false;
        return cons(j);
    }

   /* cvc(i) is true <=> i-2,i-1,i has the form consonant - vowel - consonant
      and also if the second c is not w,x or y. this is used when trying to
      restore an e at the end of a short word. e.g.

         cav(e), lov(e), hop(e), crim(e), but
         snow, box, tray.

   */
   private boolean cvc(int i) {
       if (i < 2 || !cons(i) || cons(i-1) || !cons(i-2)) return false;
      {  int ch = b[i];
         if (ch == 'w' || ch == 'x' || ch == 'y') return false;
      }
      return true;
   }

   private boolean ends(String s) {
        int l = s.length();
        int o = k-l+1;
        if (o < 0) return false;
        for (int i = 0; i < l; i++) if (b[o+i] != s.charAt(i)) return false;
        j = k-l;
        return true;
   }

   /* setto(s) sets (j+1),...k to the characters in the string s, readjusting
      k. */
    private void setto(String s) {
        int l = s.length();
        int o = j+1;
        for (int i = 0; i < l; i++) b[o+i] = s.charAt(i);
        k = j+l;
    }

   /* r(s) is used further down. */
   private void r(String s) { if (m() > 0) setto(s); }

   /* step1() gets rid of plurals and -ed or -ing. e.g.

          caresses  ->  caress
          ponies    ->  poni
          ties      ->  ti
          caress    ->  caress
          cats      ->  cat

          feed      ->  feed
          agreed    ->  agree
          disabled  ->  disable

          matting   ->  mat
          mating    ->  mate
          meeting   ->  meet
          milling   ->  mill
          messing   ->  mess

          meetings  ->  meet

   */
    private void step1() {
        if (b[k] == 's') {
            if (ends("sses")) k -= 2; else
            if (ends("ies")) setto("i"); else
            if (b[k-1] != 's') k--;
        }
        if (ends("eed")) { if (m() > 0) k--; } else
        if ((ends("ed") || ends("ing")) && vowelinstem()) {
            k = j;
            if (ends("at")) setto("ate"); else
            if (ends("bl")) setto("ble"); else
            if (ends("iz")) setto("ize"); else
            if (doublec(k)) {
                k--;
               {  int ch = b[k];
                  if (ch == 'l' || ch == 's' || ch == 'z') k++;
               }
            } else if (m() == 1 && cvc(k)) setto("e");
        }
    }

   /* step2() turns terminal y to i when there is another vowel in the stem. */
   private void step2() { if (ends("y") && vowelinstem()) b[k] = 'i'; }

   /* step3() maps double suffices to single ones. so -ization ( = -ize plus
      -ation) maps to -ize etc. note that the string before the suffix must give
      m() > 0.
   */
   private void step3() {
        if (k == 0) return;
        /* For Bug 1 */
        switch (b[k-1]) {
            case 'a':
                if (ends("ational")) { r("ate"); break; }
                if (ends("tional")) { r("tion"); break; }
                break;
            case 'c': if (ends("enci")) { r("ence"); break; }
                if (ends("anci")) { r("ance"); break; }
                break;
            case 'e':
                if (ends("izer")) { r("ize"); break; }
                break;
            case 'l':
                if (ends("bli")) { r("ble"); break; }
                if (ends("alli")) { r("al"); break; }
                if (ends("entli")) { r("ent"); break; }
                if (ends("eli")) { r("e"); break; }
                if (ends("ousli")) { r("ous"); break; }
                break;
            case 'o': if (ends("ization")) { r("ize"); break; }
                if (ends("ation")) { r("ate"); break; }
                if (ends("ator")) { r("ate"); break; }
                break;
            case 's': if (ends("alism")) { r("al"); break; }
                if (ends("iveness")) { r("ive"); break; }
                if (ends("fulness")) { r("ful"); break; }
                if (ends("ousness")) { r("ous"); break; }
                break;
            case 't': if (ends("aliti")) { r("al"); break; }
                if (ends("iviti")) { r("ive"); break; }
                if (ends("biliti")) { r("ble"); break; }
                break;
            case 'g':
                if (ends("logi")) { r("log"); break; }
        }
    }

    /* step4() deals with -ic-, -full, -ness etc. similar strategy to step3. */
    private void step4() {
        switch (b[k]) {
            case 'e':
                if (ends("icate")) { r("ic"); break; }
                if (ends("ative")) { r(""); break; }
                if (ends("alize")) { r("al"); break; }
                break;
            case 'i':
                if (ends("iciti")) { r("ic"); break; }
                break;
            case 'l':
                if (ends("ical")) { r("ic"); break; }
                if (ends("ful")) { r(""); break; }
                break;
            case 's':
                if (ends("ness")) { r(""); break; }
                break;
        }
    }

    /* step5() takes off -ant, -ence etc., in context <c>vcvc<v>. */
    private void step5() {
       if (k == 0) return;
       /* for Bug 1 */
       switch (b[k-1]) {
            case 'a':
                if (ends("al")) break; return;
            case 'c':
                if (ends("ance")) break;
                if (ends("ence")) break; return;
            case 'e':
                if (ends("er")) break; return;
            case 'i':
                if (ends("ic")) break; return;
            case 'l':
                if (ends("able")) break;
                if (ends("ible")) break; return;
            case 'n':
                if (ends("ant")) break;
                if (ends("ement")) break;
                if (ends("ment")) break;
                /* element etc. not stripped before the m */
                if (ends("ent")) break; return;
            case 'o':
                if (ends("ion") && j >= 0 && (b[j] == 's' || b[j] == 't')) break;
                /* j >= 0 fixes Bug 2 */
                if (ends("ou")) break; return;
                /* takes care of -ous */
            case 's':
                if (ends("ism")) break; return;
            case 't':
                if (ends("ate")) break;
                if (ends("iti")) break; return;
            case 'u':
                if (ends("ous")) break; return;
            case 'v':
                if (ends("ive")) break; return;
            case 'z':
                if (ends("ize")) break; return;
            default:
                return;
       }
       if (m() > 1) k = j;
    }

    /* step6() removes a final -e if m() > 1. */
    private void step6() {
        j = k;
        if (b[k] == 'e') {
            int a = m();
            if (a > 1 || a == 1 && !cvc(k-1)) k--;
        }
        if (b[k] == 'l' && doublec(k) && m() > 1) k--;
    }

    /** Stem the word placed into the Stemmer buffer through calls to add().
     * Returns true if the stemming process resulted in a word different
     * from the input.  You can retrieve the result with
     * getResultLength()/getResultBuffer() or toString().
     */
    public void stem() {
        k = i - 1;
        if (k > 1) {
            step1();
            step2();
            step3();
            step4();
            step5();
            step6();
        }
        i_end = k+1;
        i = 0;
    }

}
